Striking apparatus for rotating wheel printer

ABSTRACT

Striking apparatus for a rotating wheel printer where the striking apparatus includes a hammer mounted on one end of a lever having an intermediate semicircular bearing portion mated with a pin where the bearing is maintained in engagement with the pin by a biasing spring. An exciter includes a ram for impacting against the lever to move the hammer into contact with the printing wheel, the ram extending from a disc of magnetic material which is normally retained in the rest position by a permanent magnet but is attracted by a cup-core type electromagnet for causing the exciter to impact the lever to rotate the hammer into contact with the printing wheel.

United States Patent Bagland, III et a1.

[54] STRIKING APPARATUS FOR ROTATING WHEEL PRINTER [72] Inventors: Evan L. Bagland, III, Atherton; Robert L. Wagner, Menlo Park,

both of Calif.

[73] Assignee: American Regital Corporation, San

Carlos, Calif.

[22] Filed: May 4, 1970 [21] Appl. No.: 34,323

7 52 US. Cl. ..101/93 C, 197/49 [51] Int. Cl ..B4lj 9/00, B41j 1/22 [58] Field of Search ..101/93 C, 109, 111; 197/49, 197/23, 38

[56] References Cited UNITED STATES PATENTS 3,354,816 11/1967 Giannuzzi ..101/93 C 3,349,696 10/1967 Potter 101/93 C 3,156,180 11/1964 Barnes ..101/93C 3,308,749 3/1967 Dowd ..101/93 C 3,209,682 10/1965 Cooper et a1. ..101/109 3,001,469 9/1961 Davis et a1. ..101/93 C [451 Oct. 10,1972

3,072,045 1/1963 Goin ..101/93 C 3,1 10,250 11/ 1963 Fradkin ..197/49 X 3,135,195 6/1964 Potter ..101/93 C 3,172,352 3/1965 Helms ..101/93 C 3,266,418 8/1966 Russo ..101/93 C 3,504,623 4/1970 Staller ..101/93 C 3,643,594 2/ 1972 Pipitone 101/93 C Primary Examiner-William B. Penn Attorney-Flehr, l-lohbach, Test, Albritton & Herbert [57] ABSTRACT Striking apparatus for a rotating wheel printer where the striking apparatus includes a hammer mounted on one end of a lever having an intermediate semicircular bearing portion mated with a pin where the bearing is maintained in engagement with the pin by a biasing spring. An exciter includes a ram for impacting against the lever to move the hammer into contact with the printing wheel, the ram extending from a disc of magnetic material which is normally retained in the rest position by a permanent magnet but is attracted by a cup-core type electromagnet for causing the exciter to impact the lever to rotate the hammer into contact with the printing wheel.

10 Claims, 2 Drawing Figures STRIKING APPARATUS FOR ROTATING WHEEL PRINTER BACKGROUND OF THE INVENTION The. present invention is directed to striking apparatus for a rotating wheel printer.

In printing with a rotating wheel which has on its circumference the characters to be printed, the characteristics of the hammer that pushes the paper against the wheel are very critical. For example, the flight time of the hammer from the moment of its activation to impact must be constant and repeatable; otherwise the printed line of type will not be straight and characters may not be accurately printed.

Since bearing wear normally shifts flight time, prior devices have sought to minimize it by designs where the hammer is in the form of a projectile guided by a channel. Such devices have not proved as reliable as anticipated and are bulky, expensive and may have a low speed of operation.

Mechanically detented devices have also been provided. Here wear is again a serious problem.

OBJECTS AND SUMMARY OF THE INVENTION It is, therefore, a general object of the invention to provide an improved striking apparatus fora rotating wheel printer. I g I It is another object of the invention to provide apparatus as above which has a repeatable flight time.

It is another object of the invention to provide apparatus as above which minimizes the effects of bearing wear.

It is another object of the invention to provide apparatus as above which has a relatively large bearing area for a given mass.

In accordance with the above objects there is provided striking apparatus for a rotating wheel printer. This apparatus comprises lever means having a hammer mounted on one end juxtaposed with the wheel .and an intermediate bearing. Bearing shaft means are adapted to mate with the bearing. A mechanical exciter is supported for movement from a rest position to impact the lever means between the bearing and hammer on the opposite side of the lever means relative to the bearing to cause the hammer to move toward the wheel. Biasing means are coupled to the other end of the lever means for maintaining the bearing in contact with the bearing shaft means. Means are provided for retaining the exciter in the predetermined rest position. Actuator means propel the exciter means from the rest position to impact the lever means and mechanical stop means stop the motion of the exciter means and allow the hammer to free fly toward the wheel.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of apparatus embodying the invention; and

FIG. 2 is a cross sectional view substantially taken along the line2--2 of FIG. 1.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 illustrates a rotating wheel printer where a printing wheel has embossed upon its periphery a number of characters 11. In the case of a helical type printer the characters 11 are arranged in helix and the wheel which is mounted for rotation on a carriage is moved transverse along its axis on a rod 13. This is at a speed which is proportional to pitch of the helix.

Striking apparatus generally indicated at 14 includes a hammer 16 which is juxtaposed with the periphery of wheel 10. The hammer unit 14 is similarly mounted on a shaft 17 for transverse movement, as indicated by the arrow 18, in unison with carriage 12. Sheet material or paper 19 is placed between printing wheel 10 and hammer 16 and printing occurs when the hammer impacts paper 19 on wheel 10. Shaft 13 and 17 are mounted on a frame 21. The foregoing structure is shown in greater detail in a copending application entitled Double Helical Printer the name of Evan Ragland. As described in'that application in the case of a helical printer the striking apparatus 14 and rotating wheel 10 are continuously moved in synchronism. However, the present invention is equally applicable to other wheel printing devices such as the type where the wheel and striking apparatus are indexed for each column of print.

The striking apparatus is shown in clearer detail and in partial cross sectional form in FIG. 2 where the hammer 16 is mounted on the end 22a of a lever 22. On an intermediate portion 22b of lever 22 is an arcuate or semicircular cutout portion 23 which serves as a bearing. This mates with 'a bearing shaft or pin 24 fixed to a suitable frame better shown in FIG. 1 which mates with the bearing 23. Thus, lever 22 rotates about the axis of shaft or pin 24.

Biasing means in the form of a compression spring 26 is coupled to other end 22c of lever 22 for maintaining bearing 23 in engagement with shaft 24. One end of spring 26 is in inset portion 27 of lever 22 and the other end rests against a cup-core type electromagnet 28.

Support means 29 abut end portion 22a of the lever to resist the bias of spring 26. Thus, the bearing 23 is maintained in engagement with pin 24 solely by the spaced parallel forces on opposite sides of the bearing, or on opposite ends 22a and 220 of the lever provided by the spring biasing means 26 and by the support means 29.

' A mechanical exciter generally indicated at 31 is supported for movement from a rest position to impact lever 22 at a portion 32 on the lever which is between the bearing 23 and hammer l6 and on the opposite side of the lever relative to bearing 23 and pin 24. Such impact causes the hammer 16 to move toward the printer wheel, a portion thereof being indicated at 10. The exciter includes a ram portion 33 having a tungsten carbide extension 34 which impacts lever 22 at the portion 32 which itself is hardened tool steel. Ram 33 extends from a disc of magnetic material 36 and is adjustably affixed to the disc by an adjustable nut arrangement 37. In other words, ram portion 33 may be positioned along its axis relative to disc 36. Ram 33 is supported for movement in a self-lubricating sleeve 38 which is retained by the casing of cup-core 28.

The exciter 31 is normally retained in a predetermined rest position by permanent magnet means 39 which includes a cup shaped structure 40 of non-magnetic material having within it an annularly shaped permanent magnet 41 with appropriate polarities being material. Both the cup core 28 and disc 36 are slotted' to prevent any eddy currents. The face 44 of cup core 28 forms a stopping surface for disc 36 to limit the travel of ram 33. Thus, the stopping surface 44 is an integral part of the actuator means for actuating the exciter into impact with lever 22.

OPERATION Initially the ram 33 is adjusted by adjustable nut 37 with respect to disc 36 so that in a rest position the extension 34 is a predetermined distance away from lever 22. This is to ensure that there is no contact in the rest position with the lever. The spacing of the end of extension 34 from lever 22 is however less than the spacing 46 of the bottom of disc 36 from the stopping surface 44 of the cup core 28. This insures that impact will take place before disc 36 is stopped. Spacing 46 in the preferred embodiment is of the order of 0.014 inches.

After disc 36 is stopped by surface 44 lever 22 still free flies a predetermined distance into impact with wheel 10. This free flight allows for easy rebound of the hammer 16 from the wheel. Typical distances for the free flight zone in the preferred embodiment are 0.040 inches with 0.100 inches being the distance that the hammer 16 is moved with the exciter in contact with lever 22. Such distances are respectively indicated at 47 and 48.

Deactivation of the electromagnet 28 allows the striker unit 31 and disc 36 to again be retained in its rest position by permanent magnet 39.

The semicircular half bearing 23 of lever 22 in addition to eliminating excess weight which would occur with a full bearing also minimizes the effects of bearing wear. Because of the particular biasing by spring 26, bearing wear when it occurs merely somewhat deepens the semicircular recess 23 and because of the eveness of the wear no wobble is produced as would be the case with a full bearing in other types of actuating devices. Moreover, the placement of the ram portion 33 on the opposite side of the bearing as opposed to the biasing spring 26 also provides for more even wear. The mass of the lever 22 is also reduced since a full 360 bearing would in effect double the thickness of the intermediate lever portion 22b. Thus the arcuate 180 bearing formed by a cutout in a surface of the lever provides a large bearing area in relation to the mass of the lever.

Thus, the present invention has provided an improved striking apparatus for a rotating wheel printer which because of the minimization of bearing wear has a repeatable flight time to provide for accurate printing.

We claim:

1. Striking apparatus for a rotating wheel printer comprising: lever means having a hammer mounted on one end juxtaposed with and spaced from said wheel and an intermediate bearing; bearing shaft means adapted to mate with said bearing; a mechanical exciter including a ram portion extending from a disc of magnetic material, said ram and disc being supported from movement from a rest position to a position in which said ram portion impacts said lever means between said bearing and said hammer on the opposite side of the lever means relative to said bearing to cause said hammer to move toward said wheel; biasing means coupled to the other end of said lever means for maintaining said bearing in engagement with said bearing shaft means; means for retaining said exciter in said predetermined rest position; actuator means for propelling said exciter means from said rest position so that the ram portion impacts said lever means, said actuator means including a normally de-energized electromagnet through which said ram portion is slidably mounted, said electromagnet when energized attracting said disc to cause said ram to impact said lever means; and mechanical stop means for stopping said motion of said exciter means before said hammer reaches said wheel to allow said hammer to free fly toward said wheel.

2. Apparatus as in claim 1 where said means for retaining said exciter in said rest position includes permanent magnet means for attracting said disc to said rest position and maintaining said disc in said position.

3. Apparatus as in claim 1 where said bearing includes an arcuate portion of substantially formed in one face of said lever means.

4. Apparatus as in claim 1 together with support means where, said bearing is maintained in engagement with said bearing shaft means solely by spaced parallel forces on opposite sides of the bearing provided by said biasing means and by said support means engaging said lever means.

5. Apparatus as in claim 1 where said stop means is an integral part of said actuator means said stop means including a face of said electromagnet which forms a stopping surface for said disc when attracted by said electromagnet.

6. Apparatus as in claim 1 where said bearing includes an arcuate cutout portion formed in one face of said lever means whereby a large bearing area is provided relative to the mass of said lever means.

7. Striking apparatus for a rotating wheel printer comprising: lever means having a hammer mounted on one end juxtaposed with and spaced from said wheel, and an intermediate bearing formed in one face of said lever means by an arcuate cutout portion of substantially 180said one face forming an elongated planar surface extending substantially from said bearing to said one end; shaft means mating with said bearing, the center of said shaft means substantially lying in a plane formed by said elongated planar surface of said lever means whereby a large bearing area is provided relative to the mass of said lever means; a mechanical exciter for impacting said lever means between said bearing and said hammer on the opposite side of the lever means relative to said bearing to cause said hammer to move toward said wheel; normally de-energized electromagnetic actuating means in which said exciter is slidably mounted, said actuating means when energized propelling said exciter to impact said lever means; support means for contacting said opposite side of said lever means near said one end and biasing means coupled to the other end of said lever means, said biasing for attracting said disc and retaining said exciter in a predetermined rest position.

9. Apparatus as in claim 8 where said normally deenergized electromagnetic means attracts said disc, when energized, from said permanent magnet means for propelling said exciter to impact said lever means.

10. Apparatus as in claim 7 where said biasing means is a compression spring having one end inset in said end of said lever means. 

1. Striking apparatus for a rotating wheel printer comprising: lever means having a hammer mounted on one end juxtaposed with and spaced from said wheel and an intermediate bearing; bearing shaft means adapted to mate with said bearing; a mechanical exciter including a ram portion extending from a disc of magnetic material, said ram and disc being supported from movement from a rest position to a position in which said ram portion impacts said lever means between said bearing and said hammer on the opposite side of the lever means relative to said bearing to cause said hammer to move toward said wheel; biasing means coupled to the other end of said lever means for maintaining said bearing in engagement with said bearing shaft means; means for retaining said exciter in said predetermined rest position; actuator means for propelling said exciter means from said rest position so that the ram portion impacts said lever means, said actuator means including a normally de-energized electromagnet through which said ram portion is slidably mounted, said electromagnet when energized attracting said disc to cause said ram to impact said lever means; and mechanical stop means For stopping said motion of said exciter means before said hammer reaches said wheel to allow said hammer to free fly toward said wheel.
 2. Apparatus as in claim 1 where said means for retaining said exciter in said rest position includes permanent magnet means for attracting said disc to said rest position and maintaining said disc in said position.
 3. Apparatus as in claim 1 where said bearing includes an arcuate portion of substantially 180* formed in one face of said lever means.
 4. Apparatus as in claim 1 together with support means where, said bearing is maintained in engagement with said bearing shaft means solely by spaced parallel forces on opposite sides of the bearing provided by said biasing means and by said support means engaging said lever means.
 5. Apparatus as in claim 1 where said stop means is an integral part of said actuator means said stop means including a face of said electromagnet which forms a stopping surface for said disc when attracted by said electromagnet.
 6. Apparatus as in claim 1 where said bearing includes an arcuate cutout portion formed in one face of said lever means whereby a large bearing area is provided relative to the mass of said lever means.
 7. Striking apparatus for a rotating wheel printer comprising: lever means having a hammer mounted on one end juxtaposed with and spaced from said wheel, and an intermediate bearing formed in one face of said lever means by an arcuate cutout portion of substantially 180*said one face forming an elongated planar surface extending substantially from said bearing to said one end; shaft means mating with said bearing, the center of said shaft means substantially lying in a plane formed by said elongated planar surface of said lever means whereby a large bearing area is provided relative to the mass of said lever means; a mechanical exciter for impacting said lever means between said bearing and said hammer on the opposite side of the lever means relative to said bearing to cause said hammer to move toward said wheel; normally de-energized electromagnetic actuating means in which said exciter is slidably mounted, said actuating means when energized propelling said exciter to impact said lever means; support means for contacting said opposite side of said lever means near said one end and biasing means coupled to the other end of said lever means, said biasing means and said support means providing spaced parallel forces while said lever means is in a rest position to maintain said bearing in engagement with said shaft means, said biasing means in combination with said exciter maintaining said bearing in continuous and full engagement with said shaft means during movement from said rest position when said hammer is moving toward said wheel.
 8. Apparatus as in claim 7 where said exciter includes a ram portion extending from a disc of magnetic material and together with permanent magnet means for attracting said disc and retaining said exciter in a predetermined rest position.
 9. Apparatus as in claim 8 where said normally de-energized electromagnetic means attracts said disc, when energized, from said permanent magnet means for propelling said exciter to impact said lever means.
 10. Apparatus as in claim 7 where said biasing means is a compression spring having one end inset in said end of said lever means. 